Fluid bed processes have been employed for many years, and provide superior heat and mass transfer characteristics. For example, in an FBSG process it is known to produce synthesis gas (hydrogen and carbon monoxide) from low molecular weight hydrocarbons, primarily methane, reacted in the presence of steam, or both steam and oxygen at high temperature in a fluidized bed of catalyst, e.g. nickel-on-alumina, or admixture of catalyst and a solids diluent to moderate and control the heat of reaction.
In conducting such processes, reaction temperatures generally range about 1500.degree. F. to about 1900.degree. F. and higher, typically from about 1700.degree. F. to about 1800.degree. F.
The reactors thus operate at temperatures well above about 1000.degree. F., a temperature at which ordinary steel becomes structurally weak, and mechanically unsound; and the difficulties of such operations are increased as temperatures are increased above about 1000.degree. F.
Protection of the outer shell of the reactor from contact with gases at these high temperatures is essential, and it is required that the inside face, or internal side of the shell enclosing the intensely hot reaction zone be lined with a thermally insulating material, or refractory. A commonly used refractory material is, e.g., firebrick constituted of silica and alumina plus impurities. Often, for very high reaction temperatures the silica content or the alumina content is increased, one component relative to the other; forming a silica brick or an alumina brick (sillimanite, mullite, or fused corundum). Commonly used construction materials or liners of mechanical strength, thickness, and insulation quality sufficient for lining the internal walls of reactors to withstand these high temperatures, it has been found, thus all too often contain impurities; compounds many of which interfere with the normal operation of the process and decrease process efficiency. Silica, SiO.sub.2,is for example a contaminating compound which even in small concentration is leached from the liner by the steam to severely deactivate the catalyst, and cause serious catalyst agglomeration. Other impurities often found in such refractory materials and liners are, e.g., phosphorous and sulfur; both like silica known catalyst poisons which are leached from the liner to contaminate the catalyst.